472 Geological Society: — 



saturated by water derived from melting snows, and so were caused 

 to flow en masse down the mountain-slopes and over the gently 

 inclined ground at their base. 



The caves and fissures of Gibraltar were then described. It was 

 shown that the true bone-breccias were confined to these. Many of 

 these fossiliferous breccias are of later date than the great agglo- 

 merate, since they are met with in fissures and caves that intersect 

 the limestone and limestone-agglomerate alike. When the mam- 

 malia tenanted Gibraltar, Africa and Europe were united, and the 

 climate was genial. 



All round the rock occur platforms, ledges, and plateaus, which 

 are evidently the work of the sea. These erosion-terraces are 

 covered in many places with calcareous sandstones containing recent 

 species of Mediterranean shells. Such marine deposits occur up to 

 a height of 700 feet. The movement of depression was interrupted 

 by pauses of longer or shorter duration ; and the climatic conditions 

 .were probably much the same as at present. 



After the rock had been reelevated, the subaerial forces modified 

 the surface of the marine sands that covered the limestone plat- 

 forms, so that they came to form long sand-slopes. The land at this 

 period was of greater extent than it is now, and some grounds exist 

 for believing Europe to have been again united to Africa; for 

 mammalian remains occur here and there in the deposits that overlie 

 the limestone-platforms. These relics, however, it is just possible, may 

 be derivative. The climate was probably still genial, like the present. 



Overlying the marine and subaerial deposits just referred to 

 occurs an upper and younger accumulation of massive unfossiliferous 

 limestone agglomerate. This deposit the authors believe to owe its 

 origin to severe climatic conditions. After the marine deposits that 

 cloak so much of the eastern side of the rock had been weathered 

 into subaerial sand-slopes, large blocks were detached from the cliffs 

 and steep slopes ; and these dropped down upon the sand and were 

 soon drifted over. . By-and-by the blocks fell in such quantities that 

 the sand- slopes in many places were completely buried under a 

 talus of limestone debris. This was subsequently consolidated by 

 infiltration into a solid agglomerate, in the same way as the under- 

 lying sands were hardened into sandstone. These sandstones con- 

 tain a few blocks of limestone only in their upper portions. In 

 their horizontally bedded and lower-lying portions no limestone 

 blocks occur. 



This later agglomerate bears every stamp of great antiquity, and 

 could not have been formed under present geographical and climatic 

 conditions. The surface is honeycombed and worn, just like that of 

 the solid limestone and the older limestone-agglomerate. Since its 

 accumulation the climate has greatly changed, the present being 

 characterized by the absence of frost. 



In concluding the authors discussed at length the cause of the 

 cold conditions that gave rise to the great limestone agglomerates, 

 and argued that this cause could not have been elevation of the land. 

 They also pointed out that a submergence of the Sahara would be 



